Telephone exchange system



July 2,' G. N. SAUL TELEPHONE EXCHANGE SYSTEM Filed May 12, 1953 3 Sheets-Sheet l IHI' INVENTOR G. M 5/4 UL A TTORNEY TELEPHONE EXCHANGE SYSTEM v Filed May 12, 1933 3 Sheets-Sheet 2 ATTORNEY TELEPHONE EXCHANGE SYSTEM Filed May 12, 1955 s Sheet-Sheet s i/NVENTOR G. N. SA UL A TTORNEV Patented July 2, 19 35 UNITED STATES PATENT OFFICE I 2,006,483 I TELEPHONE EXCHANGE SYSTEM 7 George N; Saul; Brooklyn, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New

York, N. Y.,a corporation of New York Application Ma 12,1933, Serial No. 670,714

4 Claims. (cine-41 This invention relates to telephone systems and more particularly to trunk circuits terminating atv a toll operators position.

In present day telephone practice. trunk circuits both incoming to and outgoing from atoll board are arranged for direct current supervision, whereas the regular cord circuits'used at some toll positions are so arranged that but one end can be used with trunk circuits, the other end of such cords being adapted for magneto supervision only, i. e., for use only with magneto toll lines. 7 It is often desirable that a toll operator be able to complete a connection between two trunk circuits by means of one of her regular cord circuits- This, however, is not possible with present standard toll cordsof the type mentioned.

An object of the present invention, therefore, is to permit the operative connection of a magneto cord circuit to a direct current supervision trunk line. 1

Another object of the invention'is to enable a toll operator to connect two direct current supervision trunk circuits'bymeans of a cord circuit oneend of which is arranged for magneto supervision only. 1

A feature of the invention whereby the foregoing objects are attained-resides in the provision of an auxiliary circuit including a jack which is associated .with the conductors of an outgoing 30.: trunk circuit and so arranged that when, the magneto or toll end of a cord is inserted in the auxiliary jack current supervisory signals transmitted over the trunk from the distant end will be received in the auxiliary circuit, translated into alternating ringing current, and transmitted into the toll cord to control magneto supervisory signal apparatus associated therewith.

A further feature residesin filter means associated with the auxiliary circuit for the purpose intensity of, the ringing current whereby annoyance to the operator is reduced in case she'is connected to the cord at the time the ringing current is transmitted backinto the cord and also to prevent operation of ringing responsive appa-' to. Fig. 1 of which shows atoll switching trunk outgoing from a toll operators position to a distant common battery manual switchboard and arranged with an auxiliary jack and circuit in accordance with the present invention;

Fig.2 represents a toll switching trunk outgoing the provision of-this invention, insert the leftof eliminating harmonics in, anddecreasing the of relay IOI, contacts Ill. and 'right-handwind from a toll operators; position to a distant autor matic exchange also arranged. with. an, auxiliary I jack and circuit in accordance with this invention; and I V Fig. 3 represents a standard toll operators cord 5 circuit, the left-hand end of which is arranged for magneto supervision only and the right-hand end for either magneto or common battery supervision. i For purposes of description, it will first be assumed that the toll operator has received a call for a subscriber in a distant exchange and has obtained a connection with the callingsubscribers line over atoll switching trunk SWT shown at the right of Fig. 3 by inserting the trunk plug 300 of her cord pair into the jack H0 of the trunk. If the call is t'o'be extended over another switching trunk, Fig. 1,'to a distant common battery manual switchboard the toll operator may, by

20; hand or magneto plug 302 of her cord pairdirect lyinto the auxiliary-jack I00 of the trunk circuit shown on Fig. 1 which trunk extends to the desired manual switchboard, not shown. 1 When the plug 302 is inserted in'jaek I00 relays IM and 302 operate in the'following circuit, battery, left winding of sleeverelay 303, sleeve oi plug 302 and jack l00,winding of relay- I0 I, ground at the outermost left contact of relay I02. Operation of relay 303 causes relay 304 to operate thereby preventing supervisory lamp 305 from lighting at this time. When relay I M operated it (a) completes, at'its contact 03, a ringing bridge consisting of relay I04, retard coil I05 and condensers I I26, I01 and I08 across 'the tip and ring of the trunk circuit; (b) completes atv its contacts I 09, a supervisory bridge consisting of relay H0 and windings of retardcoil III across the trunk; (0) looks to ground at its inner right contacts independent of'relay I02; (d) connects battery at its outer left contact through resistance II2 to the right-hand armature of relay I02 for 0 future use in holding relay I02 operated and, (e)' operates relay I I3 in a circuit whichcan be traced from battery, left'winding of relay H3 and contact I I4 of relay I02 to ground at contact II5 of relay IIII. Relay H3 in operating operates relay I02 in the following circuit, ground, contact II5 of relay IOI, contact II4 of'relay I02, armature and contact! Ifiof relay I I3 and left-hand winding of relay- I02 to battery. Relay I02 in operating performs the following functions (a) locks up in the following circuit, battery, left-hand contact ing of relay I02 to ground and (b) removes at its til relay IIO releases in a circuit which can be traced from battery left-hand winding of relay H3, its contacts H6, contacts of relay H0, normal contacts of ringing bridge relay I04 and contact I I8 of relay I02 to ground.

When the toll operator receives the call passing signal zip tone or is otherwise apprised oi the fact that the distant operator is ready to receivefthe call she passes the number of the desired subscribers line.

Subscribers line connected When the/distant operator inserts the plug end of the trunk into the called subscribers line battery and ground are reconnected to the trunk conductors in a well known manner and cause relay H0 to operate. Relay H3 now being released and relay I02 operated an operating cir cuit is therefore completed to cause a momentary spurt or impulse of ringing current to be con-' nected to the toll cord as follows: Operation-of relay H0 closes at its contacts the following circuit to operate slow-releasing chain relay HS. Ground, contact I I8 of relay I02, normal contacts of relay I04, contacts of relay H0, contact I20 of relay H3, contact I2I of relay I02 and winding of relay H9 to battery. Relay H9 in operating completes an energizing circuit toroperate a second chain relay, I22 which can be traced from ground,;contact H0 of relay I02; normal contacts of relay I04, contacts of relay H9, and the winding of relay I22 to .battery. Relay I22 thereupon closes its contacts to operate relay I23, the c1r-= cuit for whichcan be traced from ground, contact H8 of relay I02, normal contacts of relay I04, contacts of relay 'I22 and winding of relay I23 to battery.

Relay I23 in operating connects ringing current at its contacts I21 and I28 to the tip and ring of the tollcord through. the filter arrangement comprising resistances I24 and I25 and impedance coil I26 which reduces its intensity. This causes relay 306 in the cord circuit to operate thereby releasing relay 304 which connects ground at its back contact to complete a circuit to light supervisory lamp 305 as a ready-to-ring signal. Relay 308 also operates in an obvious circuit and locks up to ground at contact 300 of talk key 3I0 if this key is in its normal position at the time. Operation of relay 308 also provides a locking circuit for lamp 305 which will remain lighted until the operator extinguishes it by operating her talk key 3I0. If, however, the talk key in the toll cord should be in an operated position at this time when the distant subscribers line is connected; the lamp 305 will not light and relay 308 will not operate as ground is disconnected at contacts 300 'of key 3I0.

Operation of relay I23 also reoperates relay I I3 in an obvious circuit which; (a) locks up in a circuit which can be traced from battery, its lefthand winding, contacts I I6, contacts of relays I I 0 and I04 and contact IIB of relay I 02 to ground;

and (b) releases relays H9 and I22 in turn. When relay I22 releases it opens the previously described operating circuit for relay E23 which slowly releases to disconnect the ringing current from the toll cord. Relays H9 and I22 also have a slow-release characteristic and therefore release of I23 is delayed sufiiciently to permit the proper functioning of relay 305 in the toll cord to light the supervisory lamp 305 as previously described.

The reduced intensity of the ringing current transmitted to the toll cord minimizes annoyance to the operator if she happens to have her telephone set connected to the cord at that time and prevents operation of'any ringing-responsive relays that may be connected across the trunk circuit to which the other end of the toll cord may be connected at this time.

Ringing the called subscriber When the toll operator rings the called subscriber at the distant oflice by operating ringing key 30] the ringing current thus appliedover the tip and ring conductors of plug 302 and jack I00 causes relay I04, bridged across the outer contacts of relay I23, to operate which (a) opens its left-hand contact thereby removing ground from the armature of relay H0 and the springs of re- 1ays.I22 and H9 and deenergizes the left-hand winding ofrelay H3 and (b') operates relay I29 andenergizes the right-hand winding of relay H3 to hold this relay operated during the ringing interval. Relay I29 operated connects, at its contacts I30 and I3I ringing current to the trunk it being observed that the auxiliary jack I00 and: cord circuit are at this time disconnected at the outer contacts of relay I29.

When the ringing key 301 is released, relay I04 releases which in turn releases relay I20 which disconnects ringing current from the trunk. The

right-hand winding of relay 1 I3 is also deenergized but this relay does not release as the release of relay I04 reestablishes the previously traced holding circuit through its left-hand winding.

Called subscriber answers When the called subscriber removes his receiver'from the hook, battery and ground are removed from the trunk conductor in a well-known manner and the bridged relay I I0 releases which opens the holding circuit of relay H3 which in turn releases. The circuit is now in condition to respond to a disconnect signal from the distant ofiice.

Called subscriber disconnects When the called subscriber hangs up relay H0 again operates which causes the successive operation of relays H9, I22 and I23 which again connects an impulse of reduced intensity ringing current to'the toll cord which operates relay 306 and causes relay 304 to release which lights lamp 305 and operates relay 303 which looks up to'hold lamp 305 lighted under control of the talk key 3I0."

Relay I23 in operating also operates relay H3 which causes the successive release of relays H9, I 22 and I23 which latter relay disconnects the ringing current from'the cord and releasesrelay 306 thereby permitting relay 304 to again operate. 7

When the toll operator notes the lighted supervisory lamp 305 she operates her talk key 3H) thereby releasing relay 308 and extinguishing lamp 3535. She willthen challenge in the usual manner and if she receives no response willremove plug 382 from jack I09 whereupon theicircuit will restore to normal. I

Connection of trunk end of toll cord 'to trunlc Should the toll operator have occasion to connect the trunk end-of her cord circuit to the trunk shown in Fig. 1, she would insert plug 305. in the Call toan automatic exchange It will next be assumed that the toll operator has received a call for a subscriber reached over a trunk line, shown in Fig. 2, which extends to a distant automatic exchange and that she has secured a connection to the calling subscribers line by inserting the trunk plug or her cord circuit into jack of a toll switching trunk SWT. Y

The next operation in completing this connection is to set up a connection to the called subscribers line by means of dial impulses and as only the trunk end of her cord circuit is equipped for this service, and isnow in use, she will insert the trunk plug of anotherpair, corresponding to plug 3%, into the regular outgoing trunk jack 290 y of the trunk and dial in the usual manner as described in the patent to Stokely 1,653,789, patented December 27, 1927, it being understood that the cord circuit shown in Fig. 3 of this application is identical with the cord circuit shown in Fig. 1 of the above noted patent and the circuit and apparatus shown above and to the left of the broken line as of Fig, 2 ofthis application is identical with the outward end of the trunk circuit shown to the left or" the broken line in Fig. 2

of the patent referred to which represents a standard out-dialing trunk to an automatic exchange.

As this dialing omration forms no part of the present invention and is described in detail beginning in line 88 on page 2 of the Stokely patent referred to, no further description will be given here.

Called subscribers Zine reached After the called subscribers line has been seized by the final selector, which will be indicated by the lighting of the supervisorylamp of the cord used for dialing, which lamp corresponds'to lamp 3H of Fig. 3, the operator inserts plug 382 of the pair to be used in completing the connection into the auxiliary Jack 2214 and removes the plug from jack 200.

When the plug 392 is inserted in jack 204 relays 208, 3933 and 3M operate in an obvious circuit. Relay 3M operated prevents lamp 385 from lighting at this time. Relay 2538 in operating connects at its contact 299 a supervisory bridge consisting of relay 2 Iii across the trunk,connects, at its contacts 2, a ringing bridge comprising relay 3H2 across the tip and ring conductors on the auxiliary jack side or the condensers H3 and 2M and at its contact 2H5 connects battery to the sleeve of the regular jack 2% thereby making it busy. As the called subscriber has not been circuit for relay 2 it which now releases;

rung his receiver is still on the hook and battery from the distant o-fli'ce thus causing relay 2m to operate 'innnediately. Operation of relay 2&9

causes relay 2E6 to operate in acircuit extending from ground, back contact of relay 2 82, contacts of relay 2H contact 2H of relay H3 and windings ofrelay 255 to battery. Relay 2E6 operates relay 22l in an obvious circuit. Relay 22H in operating causes relay 222 to operate, which relay connects, at its contacts 223 and 22, ring ing current through the filter, comprising resistancesfiit and 225 and impedance coil 221, to

the toll cord to operate relay 3:36 which releases relay 3 3d thereby connecting ground at its back contact to light supervisory lamp 3&5 as a readyto-ring signal. Relay 398 also operates and locks up to the listeningke'y 3H thereby maintaining the listening key is the: lamp 385 lighted until actuated.

. Relay 222 in operating also operates relay through its left-hand winding which then locks up under control of relay 2 ill to ground at the normal contacts of relay 212.. Relay 258 in oper-' ating opens the previously described operating I Thereupon relay 22l releases which in turn opens the and ground are present-onthe trunk conductors circuit of relay 222 whichslowlyreleases and disconnects the ringing current from the cord.

It will be noted that the ringing current app-lied to the cord by the operation of relay 222 is reduced in intensity by the filters 225, 226 and 221 in the same manner and for the same purpose as previcusly described in connection with the trunk of Fig. 1.

' Relays Zlt and 22! are also slow-releasing so that relay 222 is held operated foran interval sufiicient to cause the proper functioning of relays 3G6, 384 and 3% in the toll cord.

Ringing the called subscriber Thetoll operator uponnotingthe lighted lamp 395 actuates listening key 3 It to extinguish it and which, as previously mentioned, was bridged v across the tip and ring conductors by the opera tion of relay 208. Relay H2 in operating energizes the right-hand winding of 'relay'2 l8 to hold this relay operated during the ringing interval and operates relay 228 which connects ringing current directly to the trunk conductors which causes the called subscribers bell to be rung. When the called subscriber answers, battery and relay 2"] releases thereby releasing relay 2H3."

Called subscriber hangs up 7 ing current to the toll cord to relight supervisory lamp 305 as a disconnect signal. Relay 222 reoperates relay 2l8 which looks up and releases relays M6 and Hi which latter relay releases relay 222.

When the toll operator operates her listening key the lamp 385 is extinguished and upon challenging on the line and finding the conversation completed, she removes plug 302 from jack 2M,

whereupon relay 2B8 releases which restores the circuit to normal.

ground is removed from the trunk conductorand- What is claimed is:

1. In a telephone system, a trunk circuit providing a direct current path between its terminals, one end terminating in a jack circuit adapted for operable connection with a common battery cord circuit, a magneto cord circuit, and an auxiliary jack circuit also associated with said one end of the trunk circuit and including means for operably connecting said magneto cord to said trunk circuit.

2. In a telephone system, a trunk line adapted to transmit direct current supervisory, signals from its inward to its outward end, cord circuits arranged for magneto supervision and including supervisory signal apparatus, an auxiliary circuit including a connecting terminal associated with said line and so arranged that said cord circuit can be connected to said trunk line, and means in said auxiliary circuit adapted to receive and translate said direct current supervisory signals into alternating current signals and transmit them over said connecting terminal to a connected one of said magneto cord circuits to operate the sup-ervisory signal apparatus associated therewith.

3. In a telephone system, an operat rs position, an outgoing direct current supervision trunk line appearing thereat, magneto supervision cord circuits at said position, an auxiliary circuit associated with the trunk conductors and including an auxiliary jack whereby one of said cord circuits can be connected to said trunk over said auxiliary circuit, and means in said circuit for translating direct current supervisory signals, received over said trunk, into alternating ringing current signals and for transmitting them over said auxiliary circuit jack to a connected one of said magneto cord circuits to control the super visory apparatus therein.

4. In a telephone system, an operators position, an outgoing. direct current supervision trunk line appearing thereat, magneto supervision cord circuits at said position, an auxiliary circuit associated with the outgoing trunk conductors and including an auxiliary jack whereby one of said cord circuits can be connected to said trunk over saidcircuit, a source of alternating ringing current, means in said auxiliary circuit responsive to direct current signals incoming over said trunk to connect said ringing current source over said jack to a connected one of said cord circuits, and a filter circuit adapted to be completed in response to receipt of said direct current signals for reducing the intensity of and suppressing the harmonics in saidringing current transmitted to said cord circuit.

GEORGE N. SAUL. 

